How Does Space Telescope Work

The German astrophysicist Hermann Oberth had a number of ideas that were considered radical for his time. Indeed, during the Twenties, he wrote several papers on space exploration, sending manned rockets into space and he also talked about putting a giant telescope into orbit around the Earth. Fortunately for Oberth, he got to see these theories become reality in the Space Race that played out in the mid-20th century.

The first of the four Orbiting Astronomical Observatory satellites, OAO-1, was launched in April 1966 but was terminated after a power failure rendered its instruments useless. The second, OAO-2, was launched in December 1968 and successfully deployed its 11 ultraviolet telescopes to become the first device to observe space from orbit. The next model, Space OAO-B, also failed, but the final OAO-3 space telescope – which was dubbed Copernicus – was the most successful in this series and included an X-ray detector, paving the way for more powerful space telescopes capable of observation in many different wavelengths.

In the wake of the hit-and-miss Orbiting Astronomical Observatories, a flurry of space telescopes has been sent up to circle our planet and, more recently, the L2 Sun-Earth Lagrange point. We’ve even managed to put one – the Spitzer Space Telescope (SST) – into solar orbit.

Some of these, like the world-famous Hubble, have been invaluable in our pursuit of astronomical knowledge. But sending anything into space is expensive: Hubble alone cost GBP 1.6 billion (USD 2.5 billion) to construct and, including the five shuttle missions required for maintenance and repair, a further GBP 4.8 billion (USD 7.5 billion) to keep it operational. Compare that to the GBP 830 million (USD 1.3 billion) it cost to build the Atacama Large Millimeter/submillimeter Array (or ALMA) – the planet’s most expensive terrestrial telescope -and you may be left wondering why we bother with the off-Earth variety. There’s a very good reason though.

In the case of Spitzer, it can take far more detailed images of celestial objects from the proximity of its solar orbit. However one of the main reasons why we send telescopes into space is to get out of Earth’s atmosphere, which selectively scatters visible light and blocks many different wavelengths of the electromagnetic spectrum, restricting our view of space. By blocking some of the ultraviolet part of the electromagnetic spectrum, X-rays and other high-energy radiation that is harmful and even deadly to most organisms, our atmosphere has enabled life to flourish on Earth. But those frequencies carry a mine of information about the cosmos and can provide images that simply can’t be captured from a terrestrial vantage point.

Since the Sixties space telescopes have become increasingly sophisticated. Among the dozens that we’ve sent into orbit – including Fermi, Planck and the three remaining space telescopes of the Great Observatories programme – the upcoming launch of the James Webb Space Telescope (JWST; named after a NASA administrator) will allow us to see farther than ever and hopefully learn even more about our universe.

Great Observatories under the microscope

Over 13 years from 1990 to 2003, NASA launched a series of four orbital telescopes that have collectively come to be known as the Great Observatories. Their origins lie back in the late-Seventies and early-Eighties when it was decided that the planned Hubble Space Telescope programme would benefit from three other telescopes, each covering different areas of the electromagnetic spectrum. Shortly after the launch of Hubble in 1990 with its eye on the visible and near-ultraviolet wavelengths, was the Compton Gamma Ray Observatory (1991). The Chandra X-ray Observatory launched third and the Spitzer Space Telescope was the final one in 2003, detecting the long wavelengths of the infrared spectrum. Only Hubble and Chandra are still in a terrestrial orbit, with Spitzer trailing the Earth in a solar orbit and Compton having been deorbited in 2000 after a gyroscope failed.